JPH0639837Y2 - Organic wastewater biological treatment equipment - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention is an organism capable of highly purifying organic wastewater such as sewage and stably obtaining clean treated water with BOD of 1 to 2 mg / l. The present invention relates to a processing device.

[Conventional technology]

Conventionally, a method in which a porous granular solid (for example, sponge), which has a specific gravity close to that of water and easily flows due to water flow, is put into an aeration tank and used as a biofilm-adhering medium is disclosed in Japanese Patent Publication No. 15683.
It is publicly known in Japanese Patent No. 9 and the like.

[Problems to be solved by the device]

The method of using a sponge or the like as a biofilm-attached medium (referred to as a medium-attached biofilm treatment) does not perform sludge return and uses an aeration tank MLVS.
Although it has the feature that the S concentration can be maintained at a high level, it has the following drawbacks when confirmed by additional tests.

Since solid-liquid separation of activated sludge that does not adhere to the medium (called floating activated sludge) is performed in the settling tank, SS carry-over from the settling tank cannot be avoided.

Floating activated sludge is fine and does not flocculate well, so sedimentation is poor, and SS carryover from the settling tank is unavoidable.

The normal activated sludge method has an excellent effect of adsorbing SS in raw water to the activated sludge flocs, but the medium-attached biofilm treatment method has weak capability, and fine SS in raw water flows into the sedimentation tank as it is. There is a strong tendency to flow into treated water without being separated by sedimentation.

Since the technology is based on the premise that the floating activated sludge is separated in the sedimentation tank after the aeration tank, the water area load of the sedimentation tank is controlled by the sedimentation of the suspended activated sludge or fine SS in the raw water. However, since the settling property of these SS is poor, the required settling tank becomes large.

The quality of treated water in the biofilm treatment method with a medium is governed by the sedimentation of suspended activated sludge, and has the same drawbacks as ordinary activated sludge.

It is an object of the present invention to provide a novel biological treatment device which can appropriately solve the above-mentioned drawbacks of the prior art.

[Means for Solving the Problems]

The present invention has an aeration tank having a raw water inflow part and an outflow part in the upper part, an air diffuser in the bottom part, and a free-flowing microbial adhesion medium coexisting therein for biological treatment. Characterized in that it comprises a treatment tank that holds a levitation material layer and a treated water outflow portion, and that the lower portion is a sedimentation portion, and that the outflow portion of the aeration tank and the sedimentation portion of the treatment tank communicate with each other. It is a biological treatment device for organic sewage.

[Action]

The operation of the present invention having the above configuration will be described below with reference to FIG. 1 by taking sewage treatment as an example.

Raw water, which is sewage that first flows out from a settling tank (not shown), flows into the aeration tank 2 in which a large number of granular microorganisms-adhering media 3 that are flowing due to a water flow generated by aeration are introduced.

Since the biofilm adheres well to the microorganism-attached medium 3 in the aeration tank 2 and the total surface area of the medium is enormous, the aeration tank 2
The microbial concentration retained within (MLVSS) can be significantly increased.

However, organisms detached from the medium and microorganisms (floating activated sludge) that grow in a suspended state without adhering to the medium will inevitably coexist, and in the aeration tank 2, the medium-attached biofilm and the floating activity will be present. Soluble BOD in sewage flowing into the aeration tank 2 is separated and removed in the presence of sludge, and NH ₄ -N
Is also nitrified.

Then, the effluent flowing out from the aeration tank 2 reaches the settling section 16 in the processing tank 11 to settle the settling SS in the water. The water from which most of the SS has been settled and removed reverses upward and enters the levitation material layer 12 in the upper part of the tank in an upward flow, excessively trapped fine SS that could not be completely settled, and is extremely clear. It becomes treated water and flows out.

Further, in the device of the present invention, the concentration of the floating activated sludge flowing into the treatment tank 11 can be made significantly lower than that of the ordinary activated sludge method, so that even if the sedimentation of the suspended activated sludge is considerably deteriorated, the floating material layer The amount of SS entering 12 is smaller than in the case of the conventional activated sludge method. That is, in the normal activated sludge method, for example, when the aeration tank MLVSS concentration is set to 6000 mg / l, the MLVSS concentration flowing into the settling tank is also 6000 mg / l,
In the device of the present invention, a high concentration of MLVSS can be easily maintained by the biofilm attached to the medium, so the aeration tank MLVSS concentration is 6000 mg / l.
Even if set to, the concentration of the floating activated sludge flowing into the treatment tank 11 is only about 500 to 700 mg / l.

Now, as the above treatment continues,
Since the SS trap amount of 12 increases and the over-resistance increases, the floating material layer 12 is washed when a predetermined over-resistance (for example, 500 mmH ₂ O) is reached.

As the cleaning method, for example, the following method can be recommended. That is,
While the treatment in the aeration tank 2 is continued, the effluent is treated in the treatment tank 11
While flowing into the inner settling section 16, air is diffused inside or under the levitation material layer 12, causing a violent gas-liquid multiphase flow in the levitation material layer 12 to violently disturb the material. By this operation, the SS and excess biofilm retained in the levitation material layer 12 are washed out, and the SS and the excess biofilm are discharged together with the cleaning drainage. It is advisable to let this cleaning waste water flow into the aeration tank 2 or the first settling tank (not shown). Thus, after the cleaning for the predetermined time, the air diffusion amount is returned to the steady state, or the air diffusion is stopped and the cleaning is finished.

As described above, the cleaning of the floating material layer 12 does not require waste of clear treated water unlike the conventional apparatus, and the production efficiency of the treated water is high.

The sludge settled and concentrated in the settling section 16 of the treatment tank 11 is
Although it does not have to be necessarily used, if it is returned to the aeration tank 2, flocs of the suspended activated sludge flowing into the sedimentation section 16 are promoted, and as a result, the sedimentation property is improved.

〔Example〕

An embodiment of the present invention will be described with reference to FIG. 1. An aeration tank 2 in which a raw water inflow pipe 1 for introducing organic wastewater such as sewage is opened.
A microorganism adhering medium 3 such as sponge, fine sand, and plastic particles, which easily flows due to a water stream, is put in the inside thereof, and an air diffuser 5 connected to a blower 4 is arranged in the lower part of the aeration tank 2. There is.

Further, the aeration tank 2 is connected to an outflow pipe 6 for a liquid that has undergone biological treatment and flows out, and the outflow port of the outflow pipe 6 in the aeration tank 2 is
It is preferable to cover with a net 7 that prevents the outflow of the microorganism adhering medium 3, and when using a small particle size such as sand as the microorganism adhering medium 3, settling separation in which the upper part of the aeration tank 2 is partitioned by a partition 8 as the outflow portion. The part 9 may be formed in advance.

11 is a treatment tank, and the upper part of the tank is filled with a levitation material such as expanded polypropylene, expanded polystyrene, wood chips, pumice, and glass microballoons with a specific gravity of less than 1.0 in water to a layer thickness of 0.5 to 2 m. The levitation material layer 12 is provided, and the upper portion thereof is covered with a water-permeable supporting member 13 such as a net to prevent the levitation material layer 12 from flowing out. Since the exposure rate of is small,
The support member 13 is not always necessary. Also, the floating material layer
Inside or below 12 is an air diffuser connected to a blower 14.
15 are deployed. The floating material layer 12 can be cleaned by increasing the air diffusion amount of the air diffusion pipe 15. Also, oxygen can be supplied to the aerobic biofilm developed on the surface of the floating material layer 12. The fine SS is effectively attached to the aerobic biofilm developed on the material surface of the floating material layer 12, and a higher SS removing effect than a simple physical effect can be obtained.

The lower part of the inside of the processing tank 11 is made to function as a precipitation part 16, and the outflow pipe 6 from the aeration tank 2 is opened in the precipitation part 16.

An overflow ronder 17 is provided at the upper part of the treatment tank 11 and a treated water outflow pipe 18 is connected thereto, while a cleaning drainage outflow pipe 20 having an opening / closing valve 19 is connected thereto, and the cleaning drainage outflow pipe 20 is aerated. It is led to the tank 2 or the first settling tank (not shown).

Reference numeral 21 is a surplus sludge discharge pipe for discharging the surplus of sludge 22 precipitated and concentrated at the bottom of the treatment tank 11 to the outside of the system, and 23 is a sludge return pipe connected between the bottom of the treatment tank 11 and the aeration tank 2. .

[Effect of device]

As described above, according to the present invention, all the drawbacks of the prior art are solved and the following remarkable effects are achieved.

The carrier overrun of SS from the settling tank is eliminated, and clear treated water is always obtained, so the water quality environmental conservation effect is remarkable.

Although the floating activated sludge that is inevitably generated in the treatment of biofilm attached to a medium does not have a good sedimentation property, according to the present invention, the SS of the treated water is not controlled by the sedimentation property of the floating activated sludge. Therefore, it is easy to manage the precipitation part.

BOD removal and NH ₄ -N nitrification are performed only in the medium-attached biofilm treatment section, so the treatment effect is stable.

Since the sedimentation area can be made smaller, the installation area can be saved.
(This is because it is not necessary to separate the suspended activated sludge only by sedimentation.) Since it is not necessary to consume the clarified treated water for washing the floating material layer, the production efficiency of the treated water is high.

Since the medium-attached biofilm treatment section is provided in the previous stage, the concentration of suspended activated sludge flowing into the sedimentation section can be reduced to about 1/10 of that in the ordinary activated sludge method. As a result, even if the settling property of the suspended activated sludge is significantly deteriorated, the SS
The load can be reduced.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of the present invention. 1 ... Raw water inflow pipe, 2 ... Aeration tank, 3 ... Microorganism attachment medium, 4,
14 ... Blower, 5, 15 ... Air diffuser, 6 ... Outflow pipe, 7 ... Net, 8 ... Partition, 9 ... Sedimentation / separation part, 11 ... Treatment tank, 12 ... Floating material tank, 13 ... Support member, 16 ... Sedimentation Part, 17 ... Overflow launder, 18 ... Treated water outflow pipe, 19 ... Open / close valve, 20 ... Wash drainage outflow pipe, 21 ... Excess sludge discharge pipe, 22 ... Sludge, 23 ... Sludge return pipe.

Claims (1)

[Scope of utility model registration request] 1. An aeration tank having a raw water inflow part and an outflow part in the upper part, an air diffuser in the bottom part, and a free-flowing microorganism adhering medium coexisting therein for biological treatment.
It is characterized in that it has a treatment material outflow part while holding a floating material layer in the upper part and a treatment tank having a lower part as a sedimentation part, and that the outflow part of the aeration tank and the sedimentation part of the treatment tank are communicated with each other. Biological treatment equipment for organic wastewater.